latte-french / transactionservice

Transaction service

Revolut Backend Task

A project which:

• implements transaction service for money transfers between the accounts
• implements RESTful API methods for managing users, accounts and transfers
• saves all data into the embedded database
• is a standalone application

How to build and launch

mvn clean install to compile the code and run tests.

The resulting transaction-service-1.0-SNAPSHOT.jar can be found in the directory:

\transactionservice\target\

You can launch it via command

java -jar transactionservice\target\transaction-service-1.0-SNAPSHOT.jar

Additional details:

1. The Spark application starts on http://localhost:8080

2. PUT and POST methods require a json as a parameter.

3. Initially 'users', 'accounts' and 'user_accounts' tables are filled with some data.

RESTful API examples:

GET account with id = 4000123412341234

curl http://localhost:8080/accounts/4000123412341234

Output:

Account(id=4000123412341234, balance=23.56, currency=RUB)

GET all accounts

curl http://localhost:8080/accounts

Output:

[Account(id=4000123412341234, balance=23.56, currency=RUB), Account(id=4000123412341235, balance=5.8, currency=USD), Account(id=4000123412341236, balance=102.13, currency=EUR)]

POST a new account which will belong to the user with id = 2

curl -H "Content-Type: application/json" -X POST -d "{\"balance\":\"5\",\"currency\":\"RUB\",\"userId\":\"2\"}" http://localhost:8080/accounts

Output:

Account(id=4000123412341237, balance=5.0, currency=RUB)

PUT an account with id = 4000123412341234, updating the balance and currency

You can also update just balance or just currency

curl -H "Content-Type: application/json" -X PUT -d "{\"balance\":\"5\",\"currency\":\"EUR\"}" http://localhost:8080/accounts/4000123412341234

Output:

Account(id=4000123412341234, balance=5.0, currency=EUR)

DELETE account with id = 4000123412341234

curl -X DELETE http://localhost:8080/accounts/4000123412341234

Output:

Account deleted

GET user with id = 1

curl http://localhost:8080/users/1

Output:

User(id=1, firstName=Alex, lastName=Smith)

GET all users

curl http://localhost:8080/accounts/4000123412341234

Output:

[User(id=1, firstName=Alex, lastName=Smith), User(id=2, firstName=Clint, lastName=Eastwood), User(id=3, firstName=Peter, lastName=Pan)]

GET all accounts of the user with id = 2

curl http://localhost:8080/users/2/accounts

Output:

[Account(id=4000123412341235, balance=5.8, currency=USD), Account(id=4000123412341236, balance=102.13, currency=EUR), Account(id=4000123412341237, balance=5.0, currency=RUB)]

POST a new user

curl -H "Content-Type: application/json" -X POST -d "{\"firstName\":\"Maria\",\"lastName\":\"Teresa\"}" http://localhost:8080/users

Output:

User(id=4, firstName=Maria, lastName=Teresa)

PUT a user with id = 4, updating his first and last names

You can also change the first or the last name separately

curl -H "Content-Type: application/json" -X PUT -d "{\"firstName\":\"Julia\",\"lastName\":\"Roberts\"}" http://localhost:8080/users/4

Output:

User(id=4, firstName=Julia, lastName=Roberts)

DELETE a user with id = 2

Be careful, it will also delete all his accounts, to imitate a real banking system

curl -X DELETE http://localhost:8080/users/2

Output:

User deleted

POST a transfer, from account with id = 4000123412341234 to account with id = 4000123412341235

In this example we transfer 5 conventional units (in the currency of the fist account). In this case, it's 5.0 RUB. It will be converted into currency of the second account (to USD).

curl -H "Content-Type: application/json" -X POST -d "{\"from\":\"4000123412341234\",\"to\":\"4000123412341235\",\"money\":\"5\"}" http://localhost:8080/transfers

Output:

Transfer(accountFromId=4000123412341234, accountToId=4000123412341235, sumToTransfer=5.0, sumTransferred=0.0755, transferredAt=2019-08-25 18:56:19.238)

GET all processed transfers

curl http://localhost:8080/transfers

Output:

[Transfer(accountFromId=4000123412341234, accountToId=4000123412341235, sumToTransfer=5.0, sumTransferred=0.0755, transferredAt=2019-08-25 18:56:19.238), Transfer(accountFromId=4000123412341234, accountToId=4000123412341235, sumToTransfer=5.0, sumTransferred=0.0755, transferredAt=2019-08-25 19:02:38.944), Transfer(accountFromId=4000123412341234, accountToId=4000123412341236, sumToTransfer=8.0, sumTransferred=0.1088, transferredAt=2019-08-25 19:02:50.752)]

Exceptions

Examples of implemented exceptions:

1. "No accounts exist in the database" - if you're trying to do sth with accounts when the 'accounts' database table is empty
2. "Account with id 5 doesn't exist" - no comments
3. "No users exist in the database" - if you're trying to do sth with users when the 'users' database table is empty
4. "User with id 7 doesn't exist" - no comments
5. "No accounts belong to the user with id = 9" - no comments
6. "Account with id 4000123412341235 can't transfer 10000 RUB, the balance is only 5 RUB" - when the balance of the first account isn't enough for transferring money
7. "No transfers exist in the database" - if you're trying to request transfers when the 'transfers' database table is empty

Test coverage

• tests for Restful API

• test for services

• E2E tests

• tests with multiple threads

Used frameworks

1. Spark for implementing the RESTful API
2. HSQLDB as an embedded database with a connection pool
3. JUnit for testing
4. Project Lombok to make the life easier
5. Some small, not well-known frameworks for load testing and making a connection pool.